I think your fondness for canned "strategy" has done you in again. It only takes 7.
Actually it was an original solution, as were my others. The fondness you note is actually my fondness for solving problems myself, the quicker the better. Setting the limit to 7 would certainly put this into the "trick question" category, like you see people pull on each other at bars. So tell us the solution you read about that does it in 7.